<?php
session_start();
require_once 'db/config.php';
require_once 'mail/MailService.php';
require_once 'includes/admin_auth.php';
require_once 'includes/webinar_schedule.php';
require_once 'includes/webinar_email.php';

admin_require_login();

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    header('Location: admin.php');
    exit;
}

$selectedWebinarId = filter_input(INPUT_POST, 'webinar_id', FILTER_VALIDATE_INT);
$selectedWebinarId = $selectedWebinarId ? max(0, (int) $selectedWebinarId) : 0;

try {
    $pdo = db();

    $sql = "SELECT a.id, a.first_name, a.last_name, a.email, a.webinar_id, w.title, w.description, w.scheduled_at, w.presenter
            FROM attendees a
            INNER JOIN webinars w ON w.id = a.webinar_id
            WHERE a.deleted_at IS NULL";
    $params = [];

    if ($selectedWebinarId > 0) {
        $sql .= ' AND a.webinar_id = ?';
        $params[] = $selectedWebinarId;
    }

    $sql .= ' ORDER BY a.created_at DESC, a.id DESC';

    $stmt = $pdo->prepare($sql);
    $stmt->execute($params);
    $attendees = $stmt->fetchAll(PDO::FETCH_ASSOC);

    if (!$attendees) {
        admin_set_flash('No active attendees were found for the selected webinar.');
        header('Location: admin.php' . ($selectedWebinarId > 0 ? '?webinar_id=' . urlencode((string) $selectedWebinarId) : ''));
        exit;
    }

    $sentCount = 0;
    $failedCount = 0;

    foreach ($attendees as $attendee) {
        $payload = webinar_build_email_payload((string) ($attendee['first_name'] ?? ''), $attendee, true);
        $result = MailService::sendMail((string) $attendee['email'], $payload['subject'], $payload['html'], $payload['text']);

        if (!empty($result['success'])) {
            $sentCount++;
        } else {
            $failedCount++;
            error_log('Correction email failed for attendee #' . (int) $attendee['id'] . ': ' . ($result['error'] ?? 'unknown error'));
        }
    }

    $scope = $selectedWebinarId > 0 ? 'selected webinar' : 'all active webinars';
    $message = "Correction email sent to {$sentCount} attendee(s) for the {$scope}.";
    if ($failedCount > 0) {
        $message .= " {$failedCount} email(s) failed to send. Check the mail log for details.";
    }

    admin_set_flash($message);
} catch (Throwable $e) {
    error_log('Failed to send correction emails: ' . $e->getMessage());
    admin_set_flash('Could not send the correction email right now. Please try again.');
}

header('Location: admin.php' . ($selectedWebinarId > 0 ? '?webinar_id=' . urlencode((string) $selectedWebinarId) : ''));
exit;